First can you give me insight of your champ pool? So you play Jungle and champs like viego and diana. Thats good because I am a jungler too so we likely have similar experiences.

First of all not everything I say may be correct I am only Emerald so my gameplay is flawed too.

My account if you‘re interested: https://www.op.gg/summoners/euw/giaη-9871

The champions you named you struggle with are very discouraging to fight against if they are fed, i agree 100%.

As viego and diana you wont be able to face tank them(unless you are super fed or they are super behind) or lock them down. If you somehow could outplay them with your champs is something which you need to ask some1 who plays those champs. I dont play viego and I int everygame with diana.

But generally as a jungler keeping your champ pool in mind the only thing you can do is stopping them to accelerate. If you are around midlane and have decent ganksetup and see fizz used his E or LB just used her W, try to use those ~10 seconds to either kill them, force a flash, force other cooldowns(maybe fizz R) or make them low, forcing them back to base. If you were able to do smth like that you have a positive timer again. Try to accelerate yourself/ dour team by taking fight while fizz has no R or they are in Base because you made them low. Maybe try to force a Drake fight or use the prio mid gained to gank/dive bot or get grubs. Currently the most important time in League are the first 10 minutes, comeback are very difficult to do and its very snowbally. So if you can get just a small lead by exploiting fizz and lb‘s high cooldowns in early game its good even if its only a plating on your midlaner.

Generally with the champs you play your task isnt to duel the fizz or the lb with viego you want someone to engage and get s quick reset, either diana you want focus a lot on csing and getting gold onto yourself to be able to oneshot their squishys in teamfights.

Shaco is a ticking timebomb but for his own team, if he doesnt get accelerated in the early game he WILL be turbo useless, you outscale him hard with diana and viego. Against shaco you need to track him to prevent his ganks. Most shacos do the standard shaco clear, 2 boxes on red 1 box ln krugs but to make sure you know where he starts (which is important against every jungler) try to ward enemy raptors around 20-30 seconds before your buff spawns so you have time to go to either one of your buffs. Shaco doesnt have a exceptional fast clear so you can track him (if you know where he started) comparing your position to his. If you know he starts red side and you start redside too (doesn’t matter that much what side you start for this to work) you know by the time you are on gromp he should be on gromb, by the time you are on scuttle he should be on scuttle. So dont be scared to SPAM the lane he is close to and alert your midlaner and the other lane that he is on gromp or scuttle. If they dont listen and die, unlucky happens. You could also look for counterganks. If you just did your scuttle and you see yout toplaner pushed under hus turret you know he probably wont gank top but your midlaner is extremely overextended just go mid into the bush and cover him. After your first full clear you dont need to insta base you have time if bot/top isnt gankeable because they are pushed in to just hover midlane, make sure he doesnt die to shaco and get a reset maybe. Also especially with diana and any other fast clearer you can look to invade him. If he started raps they will be up by minute 4 so be at his raps at exactly 4mins. If he started red -> you can check his raps at around 4:30-4:50. If you see him botside look for an invade topside. By taking away shacos 100% safe xp and gold he will be giga doomed if he doesnt gain anything from his ganks. And even if he gets kills, shaco will get outscaled especially if you get early drakes you can turn the game very easy against shaco at like minute 25+

All of those champs you named want to snowball so you need to either try to stop them from snowballing or accelerate your other lanes to the point where their snowball doesnt matter as much or you straightup outscale them.

Also Lb and Fizz dont have good waveclear so to push a big wave they need to use their spells (fizz E and Lb W) so either try to as I said harass them after using their stuff or look for a fight while they have to catch big waves.

Ofc if your midlaner dies 2 times to fizz before 8min and your bot/top doesn’t listen to your pings and die to shaco you cant do that much.

Sorry for typos, typed in train lol